The effects of certain toxic plant extracts on the larvae of colorado potato beetle, Leptinotarsa decemlineata (Say)
2001
Metspalu, L. | Hiiesaar, K. | Joudu, J. | Kuusik, A. (Estonian Agricultural Univ., Tartu (Estonia). Inst. of Plant Protection)
The influence of the extracts of Heracleum sosnowskyi, Artemisia absinthium, Artemisia dracunculus, Rheum rhaponticum, Tanacetum vulgare, Levisticum officinale and Achillea millifolium on larvae of Colorado potato beetle (CPB) was estimated. The biggest death rate (75-80 per cent) was caused by giant hogweed extract. Wormwood was also toxic, killing off 70 per cent of the first-instar larvae, but its effect diminished in each following instar, being different from control only in case of the first and second larval instars. Common yarrow proved to have low toxicity, only the number of dead first-instar larvae was bigger than in the control, but the difference was not statistically reliable. Tarragon was moderately toxic, 47 per cent of the first-instar and 43 per cent of the second-instar larvae died. The death rate of the third-instar larvae was at the same level as in the control. The larvae of the first instars did not perish during the first days, but the death rate increased in the next days of development, which indicates a growing toxication in the organism leading to death due to depending physiological failures. When the larvae of CPB were eating the treated leaves of common tansy, 24 per cent of them perished. Hot-water extract was made from lovage, and it became the most effective of all the hot-water extracts. In this variant 33 per cent of the larvae died, which was significantly greater than the control variant. The extracts from rhubarb was not toxic for the larvae of CPB
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